This invention relates to a packing material for liquid chromatography and a method of manufacturing the same. In particular, this invention relates to a packing material for liquid chromatography produced by mixing carbon black and graphitizing (carbonizing) components, granulating and further heat-treating them, as well as to a method of manufacturing the same.
As a packing material for liquid chromatography, there are conventionally used a chemically bonded type of packing material based on silica gel and a packing material based on synthetic resin. The silica gel-based packing material is relatively strong in mechanical strength and is small in swelling/shrinking characteristics against various organic solvents. Therefore, it has a high resolving power and is superior in exchangeability of eluent for analysis.
However, the silica gel-based packing material has problems in that the silica gel dissolves under the acidic or alkaline conditions and that the solubility of the silica gel in an aqueous solution becomes higher under warming, resulting in a problem in durability as a packing material. The packing material of synthetic resin, on the other hand, is known to be high in acid- and alkali-resistivity, and has a good chemical durability as a packing material. However, since the mechanical strength of the particles is small and it has a swelling/shrinking characteristics against organic solvents, it has been difficult to convert them into finer particles. In addition, care must be taken in changing the analyzing conditions when a different eluent.
As raw materials which are chemically stable and are high in mechanical strength, the following are known, i.e., graphitized carbon black (as described by P. Ciccioli and R. Tappa in "Journal of Chromatography," 206 (1981) 35-42), coke powder (as disclosed by K. Unger and H. Goetz in Japanese Published Unexamined Patent Application No. 112393/1979) and activated carbon (as described by K. Unger, P. Roumeliotis, H. Mueller and H. Goetz in "Journal of Chromatography," 202 (1980) 3-14). However, they are still in the process of studying due to their stability, lifetime and complicated manufacturing processes and, in addition, what is obtained are powders of irregular forms. Therefore, it was difficult to obtain a packing material of high column efficiency as the packing material for liquid chromatography.
Further, spherical carbon packing material is manufactured by a template method based on silica gel and is available on the market (as described by J. Knox and B. Kaur in "Journal of Chromatography," 352 (1986) 3-25). It has, however, a problem in that rod-like pyrolyzed graphite is produced as by-product due to re-adhesion of gases generated at the time of manufacturing particles, and the graphite is mixed with the spherical packing material.
Still another method is known (as disclosed by Joseph Lawrence Schmitt Jr., Philip Leory Walker, Jr., George Augustus Castellion in the Japanese Published Unexamined Patent Application No. 116193/1976) in which carbon black and graphitizing (carbonizing) binder are used to obtain porous carbon particles for catalyst carrier. However, the particle shape, particle diameters or the like are not appropriate and therefore it is difficult to use it as a packing material for liquid chromatography.